Ground water drainage system

Abstract: A ground water drainage network comprising a number of strips (50,80) for embedding in the ground and forming a water permeable network or mesh structure characterised in that each drainage strip (50,80) comprises one or more high tensile-strength fibre bundles (512,513; 812) and one or more drainage belts (514; 813), one or more of said high tensile-strength fibre bundles (512,513; 812) being embedded in a polymeric material (511; 811) by a moulding process thereby forming said strip (50,80), the said strip (50,80) having at least one recessed or channelled portion (502; 802) with the one or more water permeable drainage belts (514; 813) inserted therein.

Description: This invention relates to a ground water drainage system using an underground network with drainage strips by which a three-dimensional drainage network for diverting water can be formed in the ground, thereby allowing rain water and underground water accumulated in the ground a means of drainage for the purposes of alleviating hydraulic pressure exerted in the ground, increasing ground stability and preventing earth movements from occurring in a construction site, as example (se f.i. WO92/10615). Network materials used for ground constructions comprise a synthetic polymeric material forming a network or mesh configuration, wherein said synthetic network material is formed by elongating thin strips of polymeric material using a prestressing machine as shown in Figure 1 or fabricated from high tensile-strength polyester fibre bundles wrapped with a polyethylene layer as shown in Figures 2 and 3. The friction generated between the ground and the network prevents deformation of the ground and earth movements from occurring in a construction site. When conventional drainage networks for ground constructions are used, the resulting drainage configuration formed between the drainage network and the ground very often causes serious adverse effects on the ground system in terms of ground pressure, ground stability and earth movements in a construction site. The conventional systems installed in the ground structure in conjunction with a ground construction project allowing rain water and underground water accumulated in the ground to be drained for the purposes of alleviating hydraulic pressure exerted on the ground, increasing ground stability and preventing earth movements from occurring in the construction site typically involve the employment of underground drainage devices as shown, for example, in Figure 4, used at the bottom of said ground structure, so that water can be effectively drained from the ground system. In order to control costs, the drainage pipes installed in the ground system are typically three to four meters apart, which is undesirable in that the process of installing these pipes is tedious and water cannot be effectively removed by these pipes because of the distance between them. This causes the ground to become muddy and the ground pressure to build up quickly, resulting in earth movements in a construction site. In the light of the aforementioned problems, the present invention seeks to provide a drainage network in which each strip forming the network for use in a ground construction has one or more drainage belts for embedding in the soil to form a three-dimensional drainage network system in the ground structure for draining rain water and underground water accumulated in the ground and to thereby alleviate hydraulic pressure exerted on the ground thus increasing ground stability and preventing earth movement from occurring in a construction site. The principal object of this invention is to provide a drainage network by means of which an effective three-dimensional drainage system can be established in ground structures. Another object of this invention is to provide a drainage network that can be installed efficiently to replace typical conventional piping systems such as the so-called "French pipe" systems and by which rain water and underground water will be drained substantially completely and quickly. According to this invention there is provided a ground water drainage network comprising a number of strips for embedding in the ground and forming a water permeable network or mesh structure characterised in that each drainage strip comprises one or more high tensile-strength fibre bundles and one or more drainage belts, said one or more high tensile-strength fibre bundles being embedded in a polymeric material by a moulding process thereby forming said strip, the said strip having a recessed or channelled portion with one or more water permeable drainage belts inserted therein. This invention is further described and illustrated with reference to the drawings showing two embodiments by way of examples only. In the drawings:- Figure 1 shows a plan view of a prior art construction for a drainage system using a network formed by elongating thin strips of a polymeric material, Figure 2 shows a plan view of a prior art network fabricated using high tensile-strength polyester fibre bundles wrapped with a polyethylene layer, Figure 3 shows a cross section of the network shown in Figure 2, Figure 4 shows in perspective and in part cut-away view a prior art "French pipe" system, Figure 5 shows a perspective view of a drainage network according to Example 1 of this invention, Figure 5-1 shows a detail view of a drainage strip of the network shown in Figure 5, Figure 6 shows an exploded view of the drainage strip shown in Figure 5-1, Figure 6-1 shows a cross section of the drainage strip shown in Figure 6, Figure 6-2 shows graphically the relationships between elongation and tensile strength of several strips made of different materials, wherein A is soft steel, B is the drainage network of this invention, C is unwoven cloth and D is a resin drainage network, Figure 7 shows the drainage network of this invention according to Example 1 used in a retaining wall, Figure 8 shows a perspective view of the drainage strip of the drainage network according to Example 2 of this invention, Figure 8-1 shows a detail view of a drainage strip of the network shown in Figure 8, Figure 9 shows an exploded view of the drainage strip shown in Figure 8-1, and Figure 9-1 shows a cross section of the drainage strip shown in Figure 9. Referring now to the drawings and in particular to Figures 5 to 9-1, this invention is further described with reference to Examples. Example 1 As shown in Figures 5 and 7, the drainage network 5 according to the present invention is formed from a multiple number of drainage strips 50 in a network configuration, each strip being in parallel spaced configuration and forming a coplanar mat-like structure with transverse support backing slats 51 forming cross-bearers which may be connected to the strips 50 at the cross-over points; the connection here may be by mechanical means, such as pins, or by welding or bonding. As shown in Figures 5 and 5-1, each drainage strip 50 comprises a channelled strip 511, two pairs of high tensile strength polyester fibre bundles 512 and 513, and a drainage belt 514. Referring to Figures 6 and 6-1, the parts of the strip 501 defining the channel 502 are provided with two sets of high tensile-strength polyester fibre bundles 512 and 513 embedded in the strip 511 and, as shown in Figure 6-1, this is achieved by moulding using a moulding apparatus in which the two pairs of high tensile-strength polyester fibre bundles 512 and 513 separated by an appropriate distance are embedded in a polyethylene material. The centre of said strip 501 is equipped with channel 502 containing a drainage belt 514 inserted therein by an apparatus to thereby form the assembled drainage strip 50. A polyethylene material forms the base to contain the two sets of high tensile-strength polyester fibre bundles 512 and 513 separated by an appropriate distance between which the channel 502 is located. The high tensile-strength polyester fibre bundles 512 and 513 inside said strip 501 have excellent properties for the purpose, such as durability, UV resistance, chemical resistance, bio-resistance and tensile strength. As shown in Figure 6-2, said fibre material possesses a tensile strength comparable to steel when elongated below approximately 20%. The function of polyethylene strip 511 is to maintain the shape of said strip and to prevent said high tensile-strength polyester fibre bundles 512 and 513 from being damaged during installation. The drainage belt 514 inside the slot 502 at the centre of said strip provides the means by which surface water and underground water can be drained from the ground. The drainage network of this invention possesses the following advantages: The device has a network configuration by which said drainage network can interlock with the ground to form a unit system. Additionally, forces exerted in the ground can be transferred readily to and be borne by the drainage network which is equipped with the high-tensile strength fibre bundles. Conventional high tensile-strength materials are designed to separate the ground into layers. Such configuration is undesirable in that water and air are retained in the earth below the high tensile-strength material. As a result, not only is the earth not strengthened, the safety and stability of the entire ground system is also jeopardised. When the present network is employed, the continuity and homogeneity of the ground is not interrupted. Thus the problems described above are avoided. Example 2 As shown in Figures 8 and 8-1, the drainage network 8 pertaining to this example is formed of a multiple number of drainage strips 80 in a network configuration. As in example 1 the strips 80 are interconnected by the slats 51. As shown in Figures 9 and 9-1, said drainage strip 80 has a side channel 802 in the strip 811, one pair of high tensile-strength polyester fibre bundles 812 and a drainage belt 813. The strip 801 with one pair of high tensile-strength polyester fibre bundles 812 embedded therein and as shown in Figure 9-1 is formed by moulding using a moulding device in which the high tensile-strength polyester fibre bundles 812 are embedded in a polyethylene material. One side of said strip 801 is equipped with the channel 802, and a drainage belt 813 is inserted directly into said channel 802 in said strip 801, thereby forming said drainage strip 80. The drainage networks described in Examples 1 and 2 provide substantially identical results and are different only in the shape and configuration of the drainage strip. The drainage belt employed in the present drainage networks is a porous material that allows water to permeate freely and may be formed from polypropylene or polyethylene in the form of a foam or sponge of open-pore construction. When the drainage network 5 equipped with said drainage belt is set in the ground 72 as shown in Figure 7 as example, rain water collected and underground water can be diverted to pipes 70 and drained away quickly through gully 71 of pre-cast concrete edge 73, thereby alleviating hydraulic pressure exerted on the ground, increasing ground stability and preventing earth movement from occurring in the construction site. The network comprises a number of units 5 one above the other. The complete network is so constructed that a large sheet thereof may be rolled-up for delivery to the site and thereafter installed by unrolling. The drainage network in which the drainage belt is inserted into the drainage strip has other advantages. Specifically, ground equipped with the present drainage network can be relieved of rain water and underground water accumulations. Additionally, the installation of underground drainage pipes (French drainage pipes) can be avoided, thereby reducing construction costs. The above practical examples are specific examples of the drainage network pertaining to the present invention. However, the present invention is not limited by these practical examples alone.

Claims: A ground water drainage network comprising a number of strips for embedding in the ground and forming a water permeable network or mesh structure characterised in that each drainage strip (50,80) comprises one or more high tensile-strength fibre bundles (512,513; 812) and one or more drainage belts (514; 813), one or more of said high tensile-strength fibre bundles (512,513; 812) being embedded in a polymeric material (511; 811) by a moulding process thereby forming said strip, the said strip (50,80) having at least one recessed or channelled portion (502; 802) with the one or more water permeable drainage belts (514; 813) inserted therein. A ground water drainage network in accordance with Claim 1, characterised in that a plurality of said strips (50,80) are arranged in coplanar, spaced parallel configuration and interconnected to form a mat. A ground water drainage network in accordance with Claim 2, characterised in that said strips (50,80) are interconnected by transverse slats (51) in spaced parallel configuration. A ground water drainage network in accordance with any preceding claim, characterised in that each drainage strip (50,80) has two parallel fibre bundles (512,513; 812) extending the length thereof, said strip being formed around said bundles by a moulding process. A ground water drainage network according to any preceding claim, characterised in that said strip (80) has a recess (802) along the length of a side thereof which accommodates said belt (813). A ground water drainage network in accordance with any preceding claim 1 to 4, characterised in that said strip (50) has a channel (502) in a top surface thereof which accommodates said belt (514). A ground water drainage network in accordance with Claim 6, characterised in that two pairs of parallel fibre bundles (512 and 513) are provided one each side of said channel (502). A ground water drainage network in accordance with any preceding claim, characterised in that the network is supplied in the form of a roll and is adapted to be unrolled at an installation site. A tract of land incorporating a plurality of drainage networks according to any preceding claim, said networks being embedded in the ground in spaced coplanar vertical relationship.

Inventors: YANG JESSE, YANG, JESSE
Applicants: YANG JESSE, YANG, JESSE
Application year: 1994
Main classification: E02B11
IPC codes: E02D31, E02D3, E02B11